1. Field of the Invention
The invention relates to an oil supply apparatus for an internal combustion engine provided with a variable valve mechanism that is driven by hydraulic pressure.
2. Description of Related Art
An internal combustion engine is known that is provided with a variable valve mechanism driven by hydraulic pressure, and in which a lubricant passage that leads oil to portions that need lubricating provided in the internal combustion engine, and a hydraulic passage that leads oil to a hydraulic pressure regulating valve of the variable valve mechanism, are provided branching off from a discharge side passage of an oil pump. Also, Japanese Patent Application Publication No. 04-287815 (JP-A-04-287815), for example, describes an apparatus in which a variable throttle valve is provided in the lubricant passage of such an internal combustion engine. This apparatus increases the hydraulic pressure in the hydraulic passage by throttling the variable throttle valve when the internal combustion engine is operating in a low speed region. Other related art includes Japanese Patent Application Publication No. 07-109907 (JP-A-07-109907) and Japanese Patent Application Publication No. 2009-041445 (JP-A-2009-041445).
With the apparatus in JP-A-04-287815, the variable throttle valve is fully opened when the speed of the internal combustion engine is within an extremely low speed region that includes idling speed. As a result, while the internal combustion engine is being cranked, the hydraulic pressure may be insufficient, and consequently, the variable valve mechanism may not operate.